From the UDN case #00649142:

My team noticed a bug where sometimes when using "Undo" (Ctrl+Z usually) the BP they are working on disappears in the level. We were able to find a 100% repro case when utilizing the "Replace Actors With" option. I tested on a brand new clean project with just base 5.2.1 Unreal Engine (no modifications) on my personal machine and was still seeing the issue.

You can use any BP actors, you don't have to create new ones but new ones also cause this issue. The odd thing I noticed when testing is that if I follow the steps and replace the BP actor, then wait until Unreal does an Autosave, and then hit Ctrl+Z to undo it works perfectly.
Steps to Reproduce
  1. Create a new BP actor and add a sphere static mesh component
  2. Create a new BP actor and add a cube static mesh component
  3. Add one of them to the level
  4. Select the other in the content browser
  5. Right click in level viewport and select Replace Selected Actors With -> Selection
  6. Hit Ctrl+Z to undo the replacement
  7. Note the undo happens but the BP actor is not there, in the details panel there are no components it just says [Unnamed]

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ComponentUE - Editor - Workflow Systems
Affects Versions5.2
Target Fix5.4
Fix Commit31948013
CreatedDec 22, 2023
ResolvedMar 1, 2024
UpdatedMay 24, 2024
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